- Patients with corrected QT (QTc) interval > 480 msecs or other factors that increase the risk of QT prolongation or arrhythmic events (e.g., heart failure, hypokalemia, family history of long QT interval syndrome) including heart failure that (i) meets New York Heart Association (NYHA) class III and IV definitions or (ii) is demonstrated by an left ventricular (LV) ejection fraction < 55% on baseline echocardiogram, are excluded